Electron tube



Patented Aug. 30, 1938 ELECTRON TUBE Walter Diillenbach, Berlin-Charlottenburg, Germany, assignor to N. V. Machinerieen-en Ap- 'fiaten Fabrieken- Meaf, Utrecht, Nether- Application March 1, 1935, Serial No. 8,938

Germany March 1, 1934 9 Claims. (Cl. 250-275) The present invention relates to an electron tube for the purpose of exciting, i. e. generating, amplifying or receiving high-frequency electromagnetic oscillations, particularly oscillations of a wavelength of less than m.

The essential component parts of ultra-short wave tubes of this description are the exciting electrode system, the' frequency determining resonator connected therewith and the aerial 10 coupled with the frequency determining resonator. -With a suitably selected connection, e. g.

feed-back connection, brake-field connection or magnetron connection it is possible to reduce the damping of the resonator in consequence of the influence of the stream of electrons passing over between the electron system or to cause the resonator to be excited for producing oscillations.

As resonators the invention contemplates employing not only oscillating circuits with separated self-induction and capacity, but also such circuits, in which the self-induction and the capacity have been distributed over the conductors more or less uniformly. In the former case the resonators of the known ultra-short wave tubes are made to consist of a single wire circle as selfinductlon and the electrodes as capacity. In the secondcase parallel conductors, so-called Lecher wires are used for forming a resonator which, at a potential loop, are provided with the electrodes required for excitation. For this oscillatory effeet to be attained with a resonator of such nature, the value is decisive, in connection with which L represents the self induction, C the capacity and R the total clamping resistance over which the oscillating circuit is made to flow. In a resonator in which capacity and self-induction have been uniformly distributed over the conductors, se1f-, induction and capacity forL and C have to be inserted per cm. The value will also be referred to as wave resistance or surge impedance (W), so that instead of also W2 R- 5 may be written.

In the known resonators employed in ultrashort wave-tubes, the value in OR or of is essentially smaller than that of resonance circuits employed in high frequency technics. The cause thereof is to be found in the fact, that in the ultra-short wave resonators constructed so far, the values of C and R, in relation to the'very small self-induction L, could not be made small. Particularly the value R, being composed of the Ohms resistance, the leak resistance and the radiation resistance, above all, owing to the growing radiation losses of the resonator in conjunction with increasing frequency,'will be very large. In consequence of 'these great losses at the resonator, the potential amplitudes atthe electrodes of the tube necessary for the control of the electron stream, remain small, when compared to the D. C. potentials connected up, so that the tube will work with a low degree of efliciency only.

The object of the. present in'vention is an electron tube for the purpose of exciting electro-magnetic oscillations with the aid of a resonator, in which the drawbacks, detailed above, have been obviated. In accordance with the present invention a resonator is employed, consisting of a hollow space, limited all-round, by means of metallic, well conducting walls, the natural damping of which can be kept exceedingly small. With the aid of such a resonator construction the radiation damping, which has most to be considered, has practically been reduced to zero. Also the Ohms damping of the resonator can be kept within very small limits, if the surfaces, limiting the hollow space, are made to consist of a well conducting metal, for instance, silver or copper, whichhas been provided with a, high polish. In consequence of the special, constructive measures detailed in the examples of performance, leakage losses have also, practically speaking, been avoid-' A further characteristic feature of the present W Aug. 30, 1938. w. DALLENBACH ELEC TRON TUBE Filed May 6, 1935 2 Sheets-Sheet 1 5] WALTER 1 P5:

H lnventor: DfiB/X c H Attorneys 193& w. DALLENBACH 2,123,234

ELECTRON TUBE Filed May 6, 1935 2 Sheets-Sheet 2 Patented Aug. 30, 1938 UNITED STATES PATENT OFFICE ELECTRON TUBE lands Application May 6, 1935, Serial No. 20,089

In Germany May 7,

14 Claims.

For the purpose of generating, amplifying and receiving ultra-high frequency electromagnetic oscillations, electron tubes are known, in which a flow of electrons, exciting the oscillations, has been coupled with a resonator. This resonator is excited, on the one hand, to oscillations by the flow of electrons and, on the other hand, it exerts, in some way or other, a controlling effect, upon the flow of electrons. Experiments and calculations, now, have yielded the fact, that the excitation of the resonator, will be all the stronger, the more its damping can be reduced. Considering that in connection with ultra-high frequency oscillations every resonator, not perfectly closed, will be characterized by considerable radiation losses: Isuggested in my copending application Serial No. 8,938 that a closed hollow space serve as a resonator. In a particularly favorable design of this inventive idea, the resonator is made to consist of an outer and an inner conductor similar to a concentric conductor-line, the outer conductor being shaped like a bottle and the inner conductor being made to penetrate through the neck of the bottle into the interior of the latter.

Object of the present invention is, for this reason, an electron tube for generating, amplifying and receiving ultra-high frequency electromagnetic oscillations in accordance with my copending application Serial No. 8,938, in which, in accordance with the present invention, the generator of the tube is made to consist of a bottleshaped hollow body (outer conductor) metallically conductive on its inner face, and a body (inner conductor), metallically conductive on its outer face and penetrating through the neck oi the bottle into the interior of the hollow body.

Fig. 1 represents an electron tube with a resonator consisting of concentric and cylindrical conductors of the length M4.

Fig. 2 shows a similar tube with a resonator of the length M2.

Fig. 3 illustrates a tube, in which the resonator is made to consist of a cylinder condenser and of two single-winding torus coils, the tube being,

) moreover, provided with a special control grid.

Fig. 3a is a side elevation of the transition point of the energy lead shown in Fig. 3.

Fig. 3b is a cross sectional view through the grid section of Fig. 3.

In Fig. 1 an embodiment of the object of the present invention has been represented. I is the bottle-shaped outer conductor,'2 the bottom thereof, 3 the neck of the bottle. Through the neck of the bottle so as to project into the interior of the outer conductor, the tube-shaped inner and the inner conductor 4, is almost capacitaconductor 4 has been made to pass, its end 5, being contained within the bottle, being provided with windows or having the form of a grid and approaching the bottom of the bottle only to such extent, that no essential additional terminal capacity between inner conductor and bottom of bottle is produced. Co-axial with this inner conductor, the hot cathode 6, having, for instance, the form of a hair pin, has been disposed.

If the length of the bottle between neck and bottom approximately equals M4, the outer and the inner conductor will represent a Lecher system of the length M4 which at one end above the cylinder condenser, consistingof the bottle neck tively short-circuited. Such a hollow space as the field space between the inner and the outer conductor in the interior of the bottle, represents a particularly damping-free resonator. 20

It will, however, be necessary, that in the interior of the inner conductor, through the axis of which the current leads are made to pass, suitable cross partitions 8, consisting of metal, are provided for the purpose of detuning the inner space of the inner conductor relatively to the working frequency, thus preventing an escape of oscillation energy across the interior of the inner conductor. It will thus be possible to feed the hollow space with oscillation energy, or deprive it thereof, only through the narrow annular slit in the neck of the bottle between the inner and the outer conductor.

In view of the fact, that in consideration of the flow of electrons, a direct current potential between the inner and the outer conductor is maintained, the inner and the outer conductors are insulated from each other and supported, for example, in the neck of the bottle, by appropriate distance pieces of insulating material.

In the same way as in my copending application Serial No. 8,938, it is essential that in this instance, if a particularly low damping is required, the surfaces adjoining the hollow space are also made to possess a brilliant polish and, if necessary, provided with a coating of a well conducting metal such as gold, silver and the like. As indicated in Fig. 1 the hollow body 2 may have a coating 2a, and the inner body 4 may have a coating 40.. This coating in particular will always then be necessary if, in due consideration of vacuum-technical properties, the walls adjoining the resonator consist of a non-conductive material such as a ceramic material, or

of a material of relatively high damping prop- 55 .poise for the aerial.

erties such as vacuum fused nickel, chromium iron, chromium nickel.

Furthermore, in order to attain a particularly reduced damping, it is essential to avoid sharp edges and corners impeding the passage of high frequency currents on the surface of the hollow space. It will be seen from Fig. 1 that,- in accordance therewith, all comers and edges, characterized by the numeral 9, have been carefully rounded on. A particularly highly capacitatively short-circuit of the resonator will be attained, if the cylindrical condenser, formed by the bottle neck 3 and the inner conductor 4, is tuned to the working frequency, that is to say, made of a length M4.

In many cases it will be an advantage, as shown in Fig. 1, to form the outer conductor directly as a vacuum vessel. In this case a possible form of construction consists in providing in the annular slit, serving as conductor line, in the bottle neck, a vacuum tight insulator, for instance, in form of a glass fusing. In Fig. 1 this fusing 10 will be found at that end of the conductor line turned away from the hollow space.

The annular slit may be coupled with a further conductor line or, as shown in Fig. 1, directly with an aerial. That portion of the inner conductor 8 which is exposed between i and II along a length or about M4 is made to serve asan aerial. In connection herewith the outer conductor has been provided at the extreme end of the bottle neck with a disk l2 which is intended as counter- In order to introduce the leads for the cathode, particularly the heating lines, into the tube, without having to penetrate the outer conductor of the resonator at another point than at the bottle neck, these heating lines have been made to pass from the upper end through the inner conductor. This requires, in view of the fact that a current supply, free from high frequency, is only possible in a potential node, an extension of the aerial Ill-4| by M4. This extension is covered up by a sleeve l3 passed over it and joining the inner conductor at M and carrying at the open end a disk I5 opposite the disk 5 2. The sleeve l3 thus represents, together with that portion of the inner conductor corresponding to it, a resonator or a choke, which blocks the escape of highfrequency energy towards the current supplies for the heating of the cathode. The current leads can then, for example, be made to pass through a squash i8 and through a glass tube fused onto the inner conductor at l8. This glass tube may further be provided with the branch l1 serving for the evacuation of the tube.

An excitation of the hollow space resonator, composed of the outer conductor 1 and the inner conductor 4, through the medium or the flow of electrons, can take place, for instance, if, relatively to the cathode, the inner conductor is given a positive direct currc t potential and the outer conductor a positive or negative potential in the proximity of zero. The electrons, emanating from the hot cathode, will then pass partly directly to the inner conductor and partly through between the grid bars or through the window in the space between the inner and the outer conductor, thereby exerting an exciting effect upon the resonator and subsequently returning to the inner conductor.

The length oi the portion of the inner conductor contained in the interior of the bottleshaped conductor may also amount to an odd multiple of M4 instead of M4, so that the resonator will then be excited by the flow of electrons, passing over in one or several potential loops, in a higher harmonic. The conductor parts, being positioned between the sections HI and H may be so tuned, that they form a resonance element equivalent to half a wavelength which along that part of the length, which is not covered by the outer conductor, acts as an aerial. In order to render it possible for the current in the outer conductor to pass. over, the edges of the outer conductor adjoining the radiating portionof the inner conductor, have been provided with disks l2 and I5, rendering the capacitative passage of the current of the outer conductor possible.

Another form of performance of the inventive idea has been represented in Fig. 2. Through the bottle neck 3 the inner conductor 4 is made to pass into the outer conductor l. I and 2 are forming together a Lecher system of the length M2 being provided at its ends with condensers which represent for the oscillations'in the resonator almost a short circuit. These cylinder condensers may preferably be selected of the length M4. Also in connection with shorter lengths than M4 a short circuiting effect will already take place. In the middle part of the hollow space resonator, that is to say, in the potential loop, the inner conductor 4 is provided with a grid or window 5, through which the flow of electrons, emanating from the hair-pin cathode 6, can pass into the hollow space resonator. The current leads I have, in this instance, been run so as to be inthe proximity of the potential node of the cylinder condenser l9 and are made to pass, together with a current lead for the inner conductor, through the outer conductor through an aperture 20, to which a glass tube 2| is fused terminating in a squash for the current leads. The interior of the inner conductor has again been detuned by cross partitions 8, so that a disturbing oscillation in the interior of the inner conductor cannot take place. At the open end of the bottle neck the outer conductor is enlarged so as to form a disk l2, representing the counterpoise for the inner conductor which projects by M4 and serves as an aerial. The glass tube 24, fused on at 23, renders the neck of the tube vacuumtight. This glass tube also carries the branch for, the pump conduit. The inner conductor is supported and held fast in the bottle neck on the one hand, and in the short-circuit condenser 19 on the other hand, by means of insulators against the outer conductor. Instead of giving the hollow space condenser the length \/2, its length may amount to a multiple of M2. It will then be possible to dispose electrodes, as may be required, in one or several potential loops for excitation and to excite the resonator in the corresponding high harmonic. I

Instead of employing concentric, cylindrical conductors (so-called concentric Lecher systems) for the purpose of limiting the hollow space aiaaaae structional length and a greater oscillatory ciliciency. For the rest the arrangement corresponds to that illustrated in Fig. 2 with the only diflerence, that in place of an aerial, the open end of the bottle neck is coupled with an energy conductor line. The resonator is, like that shown in Fig. 2, composed of two elements of the length M4, so as to form a V2 resonator. Instead of making use of two resonance elements, consisting of cylinder condenser and single-winding torus coils, also a U4 resonator or an odd number of such resonators may be connected in series so as to form one resonator, which can then be excited in several potential loops by flows of electrons.

When joining an even number of resonance elements in accordance with Fig. 3, it is essential to insert in the bottom of the bottle-shaped outer conductor, in the same way as shown in Fig. 2, a short-circuit condenser 4', i9, which again may be constructed as a cylinder condenser, for example, of the length M4.

It has further been shown in Fig. 3, in what manner the tube is coupled with a conductor line extending transversely to its axis The outer conductor joins the open end of the bottle neck to the conductor 29 of a Lecher system extending perpendicularly to it, the second conductor 30 of said Lecher system being in conductive connection with the inner conductor at 32 through the medium of the sleeve 3|. The portion of the inner conductor projecting from the outer conductor I now forms, as far as it extends between the two conductors 29 and 30 or within the interior of the sleeve 3 I, together with the sleeve 3i, an element tuned to resonance, being eq iivalent to a Lecher system section of the length \/2. The two conductors 29 and 30, between which, by means of the oscillation, stationary waves or running waves on the inner conductor 4 are excited, have further been enclosed in a tube 33, in order to obviate radiation losses. The supply of current to the cathode may be effected in the same manner as in Fig. 1 through the medium of the squash i8.

Fig. 312 represents a cross sectional view perpendicular to the axis of the conductors 29 and 30 at the point of coupling with the tube.

In many cases there will be a requirement for earthing the bottle-shaped outer conductor, particularly in all those cases where it is to be firmly combined with reflector arrangements,'such as mirrors. In viewof the fact, that between cathode and outer conductor a positive or negative direct current potential prevails, generally not very much differing from zero, the cathode relatively to earth, will be given a direct current potential in all cases of the earthed outer conductor.

The arrangements in accordance with Figs. 1 and 2 may be modified without any difficulty so as to represent electron tubes for the amplification of ultra-high frequency oscillations. For this purpose, as it has been shown in Fig. 3, the oathode 6 is surrounded by a control grid 34 which is continued as a tube 35 concentrically surrounding the cathode lines 7. The elements 1 and 35, on the other hand, together again form a Lecher system, which exhibits, in place of the cathode 5, a potential loop. This Lecher system is deposited in the interior of the inner conductor 4, the inner conductor 4 and the tube 35 being so dlsposed,

obviate any possibility of parasitic oscillations within this hollow space. The oscillations excited between the concentric conductors I and 3' now yield, owing to the space charge limitation, a

. control of the stream of electrons emanating from the cathode i and penetrating into the hollow space resonator proper through the control grid 34 and the grid or window 5;

The high frequency energy required for the control of the control grid, that is, the double conductor line consisting of the elements I and 36 is, as shown in Fig. 1, made to-pass into the interior of the inner conductor through the neck of the bottle up to a potential node of an energy conductor line or a resonance element coupled with the open end of the bottle neck.

With the: aid of the arrangement detailed in Fig. 3, for the amplification of ultra-high 'frequency oscillations, it will be possible to produce thereby a self-excited generator-based on backcoupling, or a receiver with damping reduced by back-coupling. A part of the ultra-high frequency oscillation energy, escaping from the hollow space reson tor through the annular slit in the bottle neck, ill then be fed to the Lecher system composed of the conductors I and 35. The transmission of this energy can, for example, be effected, in that through the medium of suitable windows or apertures, high frequency stray fields which, by way of example, are fed by the annular slit, are made to interfere in the field zone of the Lecher system composed of the conductors l and 35, exciting said system to oscillations through the medium of field coupling.

What I claim, is:

1. An electron tube comprising, a hollow member electrically conductive on its inner surface, an inner member electrically conductive on its outer surface within said hollow member, a portion of said hollow member forming a solid-wall electrode, a portion of the inner member having openings therein, a cathode within said last named portion of the inner member, said hollow .member and inner member constituting boundaries of an oscillator having a length which is a multiple of one fourth of the desired wave length,

' and means closing said oscillator radiation tight.

2. An electron tube comprising, a cylindrical hollow member electrically conductive on its inner surface, an inner member electrically conductive on its outer surface coaxially disposed within said hollow member, a portion of the hollow member forming a solid wall electrode, a portion of the innermember having openings therein, a cathode Within said last named portion of the inner member, said hollow member and inner member limiting a cavity closed against leakage losses which forms the field space of a resonator, a concentric conductor of less diameter than, and connected to, said hollow member, and a second conductor connected to said inner member, the wave resistance of said first named conductor being small as compared with that of the resonator.

3. An electron tube comprising, a cylindrical shaped hollow member electrically conductive on its inner face, a conductive bottle neck connected with said hollow member, a cylindrical inner member electrically conductive on its outer face and extending coaxially through the bottle neck element into the hollow member and forming with the hollow member a cavity closed oif against leakage radiation, said inner member also forming with the bottle neck a high frequency lead, a 

